How can we make zero energy skyscraper a reality?
21/22 ART627 Sustainable Mega-buildings Overview MSc Sustainable Mega-Buildings
By Deepak K Sadhwani December 2021
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Table of Contents Declaration Form….………………………………………………………………………………...…1 Table of Contents…………….…………………………………………………………………...…...2 List of Figures………………………… …………………………………………………...................3 1. Introduction……………………………………………………….………………………………….4 2. Research Methodology……………………………………………………………………………..4 2. Case Studies Evaluation……………………….…………………………………………………..5 3. Conclusion…………………………………………….……………………………………………..14 4. References………………………………………………..………………………………………...15
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List of Figures Figure 1. Site Location and Masterplan………………………………………………………….........5 Figure 2. Existing high-rise developments around the site………………………….……….….......5 Figure 3. Psychometric Chart for Central Jakarta.………...………………………………………….6 Figure 4. Solar Radiation analysis for the Pertamina Campus.……………………………………..7 Figure 5. Sun Shading devices on East-West facade …………………………………………….…7 Figure 6. Sun Shading devices on North-South facade.……………………………….…….………8 Figure 7. Form Building ………………………………………………….……………………..……….8 Figure 8. Tower Structure ……………………………………………………………………………….9 Figure 9. Conceptual drawings for PET …………………………………………………………...…10 Figure 10. Architectural rendering of 99th-floor sky deck ………………………………………….10 Figure 11. Architectural Renderings of PET ………………………………..……………………….11 Figure 12. Architectural Renderings of PET …………………………………………..…………….11 Figure 13. Vantage point selection …………………………………………………………………...12 Figure 14. Skyline implications when observed from the three vantage points ………………….13 Figure 15. Understanding cultural textures of Jakarta ……………………………………………...13
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How can we make zero energy skyscraper a reality? 1. Introduction The Pertamina Energy Tower (PET) is a proposal developed by Skidmore, Owings, and Merrill LLP (SOM) for state-owned Pertamina Energy company’s office headquarter in Jakarta, Indonesia. The main goal of the project is to become the first supertall tower campus to achieve net-zero energy performance by exhibiting a variety of sustainable solutions in the process. The project combines several measures to maximize efficiency and generate on-site energy from solar, wind, and geothermal sources to reach this goal. Furthermore, the campus has a zerowater discharge target, which is met by looking at the project holistically across all disciplines. In February 2015, the financial director of Pertamina announced that further construction of the PET had to be suspended due to "depressed oil prices”. The decision to temporarily halt development was also due to the revision of the Company's Budget Work Plan (Nikkei Asia. 2015). In 2016, Cabel News Network (CNN) further reported that the proposed skyscraper will be replaced with a scaled-down 30-storey tower. (Pertamina Energy. 2016) Considering the ambition of the project, the aim of this report is to critically evaluate the conceptual design of the PET based on the following parameters: 1. Form and function of the Tower 2. Spatial planning and fit-out 3. Aesthetic, visual and skyline implications of the design 2. Research Methodology A literature study is performed by reviewing contextual and climatic data for Jakarta by using research papers, weather data, and following records of societal developments. Climate Consultant software has been used to perform weather charts like temperature, relative humidity, wind, radiation, and psychometric analysis by using a reviewed EnergyPlus weather file. The inferences from the weather data are incorporated in a Ladybug Simulation file in Grasshopper to run simulations. Radiation simulations have been performed on a building of the same scale for the PET to derive the most optimum orientation and sun-shading devices strategy. An existing CFD and structural system study done by SOM has been reviewed to analyze the form of the tower. Spatial planning has been reviewed and analyzed by preparing mock floor plans using Rhino3D and Design-Builder for daylight and illuminance. Available architectural renderings and a SketchUp model of the city of Jakarta have been used to review the aesthetic, visual, and skyline implication of the tower.
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3. Case Study Review 3.1. Site Location and Context The Pertamina campus is located along the Jalan Rasuna Said Commercial spine in Jakarta, 6°South 107°East to the equator [See Figure 1(a)]. The site is within the Rasuna Epicentrium Central Business District (70 hectares) of Jakarta with major high-rise developments in vicinity such as the current tallest building- Gama Tower (285.5M), Bakrie Tower (214M), and Trinity Tower (263M). (See Figure 2)
Figure 1. Site Location and Masterplan (a) Pertamina Campus site location, (b) PET Campus. © SOM 2021
The 6 million sq. ft. masterplan design houses the office headquarters as the focal point of a larger development that includes a performing arts and exhibition pavilion, a mosque, a central energy plant, a visitor center, and a café connected at the pedestrian level by a Photovoltaic (PV) canopy called the energy ribbon [See Figure 1(b)]. The tower is topped at a height of 523 meters with 99 habitable floors.
Figure 2. Existing high-rise developments around the site. (a) Trinity Tower, (b) Bakrie Tower, (c) Gama Tower
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3.2 Climate The tropical monsoon climate of Jakarta sees about 9 months of wet-humid conditions with daytime temperatures exceeding 30°C (>90% of the year) and reaching up to 31°C. The city receives ~1.7m of rainfall (annual average). Dry-humid conditions are observed for the remaining 2 and a half months. The city experiences high humidity (>70%) and frequent precipitation together with daytime temperatures dropping below 26°C and remaining close to comfortable values (below 30°C) on an average. Climatic conditions, therefore, remain on the warmer side for most part of the year with a brief period (about 3 months) of mild winters, with warm days and cool nights. During the summer-fall months, West and South faces receive maximum daylight whereas, East would benefit from sun shading. In the winter-spring month, East receives less daylight. Throughout the year, total surface radiation is high, with global horizontals surpassing 800 Wh/sqm for majority of the year. Jakarta's coastline location experiences high wind velocities from all directions, with wind speeds surpassing 8 m/s. The strongest wind speed was measured in January (>13 m/s) As per ASHRAE Standard 55-2004, the project site perceives zero comfortable zones in relation to temperature and relative humidity established via a psychrometric chart. The chart suggests that up to 40% comfortable hours can be achieved through sun shading and dehumidification only. However, this depends on the type of system used to achieve the desired result. Remaining 60% comfortable hours could be achieved using mechanical ventilation and lighting strategies (See Figure 3).
(a) Passive strategies
(b) Active systems
Figure 3. Psychometric Chart for Central Jakarta. (a) Passive strategies (b) Active systems
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3.3 Form and function The orientation of the tower is the first step towards maximizing environmental gain and reducing financial investment. Considering base building orientation along the direction of the sun, i.e., East-West, the façade receives a total solar radiation of 111 GWh per square meter. Rotating the building along the North-South axis reduces the total radiation by 10% (See Figure 4).
Inferencing from the psychometric chart, the tower will benefit from planning shading devices on all façades. The system can be different for East-West and North-South respectively because of the varying radiation values. Radiation on East & West facades exceeds 950 kWh per square meter. Planning horizontal shading devices will bring down the total radiation by 25% (to 82.5 GWh per square meter) of the base value, whereas vertical shading brings down the total radiation by 35% (to 75 GWh per square meter) (See Figure 5). Planning vertical shading on East-West façade will reduce the demand for mechanical systems.
Radiation on South Facade facades exceeds 950 kWh per square meter. Planning horizontal shading devices will bring down the total radiation by 61% (to 44 GWh per square meter) of the base value, whereas vertical shading brings down the total radiation by 58% (to 47 GWh per square meter) (Figure 6). Planning horizontal shading on North-South façade will further reduce the demand for mechanical systems.
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Wind movement is another factor that governs the tower form. The project site receives fierce winds from all directions. Hence, a curved form would allow for the winds to pass around or through the tower without creating major turbulence around the tower. Obstructions near the ground can significantly alter local wind conditions. A vertical channel along the East-West façade directs the wind upwards. The wind turbines were integrated within the crown of the tower at 500 meters and at sky lobbies to maximize the potential energy generation from wind [See Figure 7(a)].
Figure 7. Form Building (a) CFD (Computational Fluid Dynamics) Analysis at the top, (b) Form development for PET. © SOM 2021
The conceptual design proposal by SOM features a curved tower form oriented along the NorthSouth axis. The demand for mechanical ventilation has been reduced by using vertical sun shading devices on the East-West façade and Horizontal devices on the North-South façade. The tower is optimized by maximizing environmental gain using sun and wind as the guiding principles for the form and fabric [See Figure 7(b)].
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3.4 Spatial planning and fit-out The tower's dual system is designed to withstand substantial wind and seismic loads, while minimizing the quantity of material required and rendering other sustainability methods more accessible. The curved form of the tower is facilitated by the moment frame combined with a ductile reinforced concrete core with composite perimeter columns (See Figure 8). This is tied together by structural steel outriggers and belt trusses at every 30 floors. The load is transferred to the core and perimeter columns by the gravity system of a composite concrete slab on a metal deck supported by structural steel beams (Besjak et al. 2017). The structural system allows efficient integration of architecture and MEP services.
The public realm is accentuated by triple-height arrival spaces. The first 3 floors comprise meeting rooms and lounges overlooking the pedestrian realm along the perimeter. The 7th and 8th floors locate the data centers for the entire campus. 75 department offices are located between the three belt trusses. These intermediate floors are planned to host sky lobbies with wind turbines, refuge terraces, cafeterias, and mechanical services. 05 Executive offices are proposed above the third belt truss. The final 99th floor is divided into 3 spaces – Restaurants, Observation Deck and Wind turbine viewing at the crown [See Figure 9(a) and Figure 10].
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Outriggers are obstructive inside the floor interfering with occupiable or rentable space thereby usually limiting their placement in mechanical and/or refuge floors (Moon 2018). Offices Floorplate efficiency is described as the percentage of usable office area. It is exclusive of lift lobbies, toilets, staircases, fire tower, AHU (air handling units), electrical rooms, and all shaft cut-outs. For PET, it is limited to 65%. Services core planned at the center do not disrupt the working areas during maintenance and fit-out [See Figure 9 (b)].
Figure 9. Conceptual drawings for PET. (a) Architectural Section of PET © SOM 2021, (b) Typical Office Floorplate.
Figure 10. Architectural rendering of 99th-floor sky deck © SOM 2021
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3.5 Aesthetic, visual and skyline implications of the design Integrating a tall building into a city and within an existing skyline is a complex, yet necessary process. A range of vantage points needs to be considered as well as both the day and night views of the city (Al-Kodmany, 2011). The tower gently tapers towards the crown to frame the opening for wind turbines. The exterior fabric is designed to be predominantly glazed with clearly identifiable solar shades on the South façade to optimize natural lighting and solar heat gain (See Figure 11).
Figure 11. Architectural Renderings of PET (a) Gentle tapering of the tower towards the crown, (b) Exterior fabric showcasing solar shading. © SOM 2021
During the day, the tower’s shading devices light up with the daylight, and an orange clay texture is observed on the façade, which goes well with the cultural implications of the local Jakarta fabric (See Figure 12). At night time, the focus is on the vertical cleft at East and West, which seems to be expressed by artificial lighting all the way to the crown.
Figure 12. Architectural Renderings of PET © SOM 2021
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Three vantage points (V1, V2, and V3) have been highlighted to study the visual impact of the tower. Jakarta has two major high-rise spines planned along Jl. Jend. Sudirman and Jalan Rasuna Said Roads. V1 is a high-altitude view, assumed at the crown level heights of the towers planned along the Jl. Jend Sudirman road. V2 is from an external transportation vehicular zone of the city which has views towards all the towers planned along both the high-rise spines. V3 is assumed at the spaces between the city center and Jakarta Bay. The same can be considered as a waterfront view of the skyline. (See Figure 13)
Figure 13. Vantage point selection. (a) High-rise spines in Jakarta, (b) Vantage point locations
At V1 and the spaces around it, the PET appears to be in harmony with existing skyline of the city. Narrow spacing between most of the high-rise buildings is observed with PET forming the focal point of the overall skyline. At V2, PET synchronizes with most of the high-rise buildings along the spines and collaborate to create an interesting skyline signature. At V3, the PET can be clearly identified due to its monofocal appearance while the rest of the towers appear to be in polyfocal clusters (See Figure 14).
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Figure 14. Skyline implications when observed from the three vantage points. (a) V1- high-altitude view, (b) V2primary view from external transportation vehicular zone, (c) V3- waterfront view
The material palette seems to have been derived by taking inspiration from the local culture. A similar color tone is observed in the religious and spiritual developments around the city (See Figure 15).
Figure 15. Understanding cultural textures of Jakarta
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4. Conclusion The project design highly benefits from maximizing sun shading in East and West, and optimizing sun shading in North and South. Light-colored external shading devices may provide slight comfort in warm and humid periods. The curved form allows harsh winds of up to 15 m/s to flow smoothly along the façade minimizing the sway. Although the structural system allows for design freedom in terms of a column free floorplate, the overall efficiency of 65% is not a viable scenario for an office building. This can be increased by reducing the height of the tower to allow for a different structural system. Furthermore, PET’s sky lobbies at multiple levels helps in connecting occupants to greenery and trees. Incorporating these, the tower supplies more nature-friendly environments. Vertical foliage would also help cool the tower down by reducing the heat island effect. In terms of skyline implications, the PET is observed to be holding a central location when viewed from 2 vantage points. V3 suggests that PET will break the monotony and harmony observed from the other two. The use of clay orange materiality in the solar shading devices reflected in the South Façade does not cause visual disruption or awkwardness in the skyline. Tall structures can be sustainable; the main impediments are economic and societal, but not technological, as depicted in this report. However, geography plays a key role, as Indonesia has surplus geothermal energy available at shallow depths than the rest of the world. Geothermal energy generation is proposed to produce surplus energy than the campus's energy demand, feeding electric power from renewable sources back into the grid, thus making the project netpositive on energy. Capital costs for renewable energy sources and market acceptance are economic constraints, while visual effect, novelty, and safety are societal concerns.
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References [1] Al-Kodmany K. The Visual Integration of Tall Buildings: New Technologies and the City Skyline. (2013) The Journal of urban technology, 20 (2), p.25-44 [2] Ali M, Moon K. Advances in Structural Systems for Tall Buildings: Emerging Developments for Contemporary Urban Giants. (2018) Buildings, MDPI AG, 8 (8), p.104 [3] Besjak C, Biswas P, Petrov G, Meinschein G. New Heights in Sustainability – Pertamina Energy Tower. (2015) Structural Congress, p925-960 [4] Besjak C, Biswas P, Petrov G, Streeter M, Devin A. Effects of Perimeter to Core Connectivity on Tall Building Behavior. (2017) CTBUH International journal of high-rise buildings, 6(1), p.1-9 [5] Moon K. Supertall Asia/Middle East: Technological Responses and Contextual Impacts. (2015) Buildings, MDPI AG, 5 (3), p.814-833
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